Extruded firearm buffer tube

ABSTRACT

A lightweight, corrosion and abrasion resistant magnesium firearm buffer tube assembly, configured to lighten or otherwise reduce the overall weight of AR-10 rifles, AR-15 rifles, M-16 rifles, and variants thereof. The buffer tube assembly including a buffer tube and an endcap. The buffer tube constructed of a magnesium alloy and can have a distal end, a proximal end, and a tubular wall defining a tubular throughbore traversing axially through the buffer tube between the distal end and the proximal end. The endcap positioned at a proximal end of the buffer tube, thereby providing a buffer spring operating surface sufficient to resists reciprocation forces during operation.

RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Application No. 62/858,716 filed Jun. 7, 2019, which is hereby incorporated herein in its entirety by reference.

TECHNICAL FIELD

The present disclosure relates generally to firearm buffer tubes, and more particularly an extruded magnesium buffer tube for use in firearms including AR-10, AR-15, M-16, and variants thereof.

BACKGROUND

The ArmaLite AR-10 was developed by Eugene Stoner in the late 1950s as a lightweight assault rifle for military use. The basic AR-10 design had a direct impingement, rotating bolt configured to accept 7.62×51 mm NATO (.308 Winchester) cartridges. In 1957, the AR-10 design was rescaled and substantially modified by ArmaLite to accommodate 5.56×45 mm NATO (.223 Remington) cartridges, and given the designation AR-15. ArmaLite sold its patent rights to the AR-10 and AR-15 to Colt Firearms in 1959. After subsequent modifications, the AR-15 was adopted by the US military as the M-16 rifle. With the expiration of the ArmaLite patents in 1977, other manufacturers began producing their own variants of the firearm, commonly known as AR-15 style rifles.

Today, the AR-15 rifle has become one of the most beloved rifles in the United States, and has been referred to as “America's rifle” by the National Rifle Association (NRA). One innovative feature of the AR-15 rifle is its distinctive two-part upper and lower receiver and its modular design enabling the ease in the interchangeability and replacement of parts. As civilian ownership of AR-15 style rifles grew, numerous manufacturers began producing “improved” aftermarket modules, assemblies, or parts with features not found on factory rifles. Due to the AR-15 rifle's modular construction, individuals with an average mechanical aptitude can substitute these aftermarket parts with the original factory parts to customize their rifle. Due to the vast assortment of aftermarket parts and accessories currently on the market, the AR-15 style rifle has been referred to as the “Swiss Army knife of rifles.”

One interchangeable component or part of the AR-15 rifle is the lower receiver extension tube, commonly referred to as the “buffer tube” or “buffer tube assembly.” Referring to FIGS. 1A and 1B, an AR-15 rifle buffer tube assembly 100 of the prior art is shown. The buffer tube assembly 100 generally includes a buffer tube 102, a buffer 104, a buffer spring 106, a latch plate 108 and a castle nut 110. Typical AR-15 rifle designs include a gas tube 112 to vent burnt powder gas back into a bolt carrier assembly 114 where it expands in a variable volume chamber forcing the bolt 116 open to eject the spent cartridge case, while compressing a buffer spring 106 located in the buffer tube assembly 100. Upon maximum compression, the buffer 104 and buffer spring 106 bias the bolt 116 closed, wherein the bolt 116 picks up a new cartridge from a magazine upon closure. Accordingly, the buffer 104 and the buffer spring 106 are required to provide a surface and force which resists the rearward movement of the bolt carrier 114. The weight of the buffer 104 is selected to minimize bolt bounce and assist in the proper operation of the gas operating system.

As depicted in FIG. 1B, the buffer tube assembly 100 is fixedly coupled to the lower receiver 118, often via a threaded portion 120 defined on a distal end 122 of the buffer tube 102, which is received in a corresponding threaded aperture 124 of the lower receiver 118. The latch plate 108 and the castle nut 110, which can be positioned on the buffer tube 102 prior to connection to the lower receiver 118, can be tightened against the lower receiver 118 thereby locking the buffer tube assembly 100 in place relative to the lower receiver 118.

In battery, the rear end of the bolt carrier 114 generally resides within an upper receiver (not depicted) and abuts the front of the buffer 104. While the buffer tube 102 does not receive the entire length of the bolt carrier 114 during its reciprocating motion, the bolt carrier 114 generally extends several inches into the buffer tube assembly 100 during maximum compression of the buffer spring 106. A typical buffer tube 102 generally has a length of about 7.2 inches. A portion near a proximal end 126 of the buffer tube assembly 100 typically includes a raised rail portion 128 defining a channel 128 configured to receive an adjustable butt stock (not depicted). The butt stock is generally adjustable in length according to one or more blind bore apertures 130 defined within the raised rail portion 128.

As AR-15 rifles are commonly carried for long distances and long durations by police, hunters and sportsmen, a desire exists to lighten or otherwise reduce the overall weight of the rifle. The present disclosure addresses this concern.

SUMMARY OF THE DISCLOSURE

Embodiments of the present disclosure provide a lightweight, corrosion and abrasion resistant magnesium buffer tube, configured to lighten or otherwise reduce the overall weight of AR-10 rifles, AR-15 rifles, M-16 rifles, and variants thereof. Various apparatus embodiments and methods of manufacturing magnesium buffer tubes are disclosed herein.

One embodiment of the present disclosure provides a firearm buffer tube assembly including a buffer tube and an endcap. The buffer tube can be constructed of a magnesium alloy and can have a distal end, a proximal end, and a tubular wall defining a tubular throughbore traversing axially through the buffer tube between the distal end and the proximal end. The endcap can be positioned at a proximal end of the buffer tube, thereby providing a buffer spring operating surface sufficient to resist reciprocation forces during operation.

In one embodiment, the endcap can be constructed of a magnesium alloy. In one embodiment the endcap can be welded to the buffer tube. In one embodiment, the endcap can be threadably coupled to the buffer tube. In one embodiment, the endcap can be injection molded into the buffer tube, such that a portion of the endcap extends through an aperture defined in the tubular wall, thereby inhibiting axial movement of the endcap. In one embodiment, the endcap can be formed by bending a proximal portion of the tubular wall at an angle with respect to a longitudinal axis of the buffer tube to provide the buffer spring operating surface. In one embodiment, the endcap defines a throughbore aperture configured to enable venting of gas in the tubular throughbore during operation.

In one embodiment, at least portions of the firearm buffer tube assembly include an anodized surface coating configured to impart improved abrasion resistance and/or increased surface lubricity. In one embodiment, at least one of micro-sized industrial diamond particles, nano-sized industrial garnet particles, silicon carbide, aluminum oxide, microsized Teflon™ spheres and/or molybdenum disulfide are integrated into the anodized surface coating.

Another embodiment of the present disclosure provides a method of constructing a firearm buffer tube assembly, including the steps of: extruding a magnesium alloy buffer tube having a distal end, a proximal end, and a tubular wall defining a raised rail portion extending along a longitudinal axis of the buffer tube, and a tubular throughbore traversing axially through the buffer tube between the distal end and a proximal end; removing a portion of the raised rail portion in proximity to the distal end of the buffer tube; defining external threads in proximity to the distal portion of the buffer tube; blocking a portion of the tubular throughbore in proximity to the proximal end of the buffer tube via an endcap, thereby providing a buffer spring operating surface sufficient to resist reciprocating forces during operation.

The summary above is not intended to describe each illustrated embodiment or every implementation of the present disclosure. The figures and the detailed description that follow more particularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be more completely understood in consideration of the following detailed description of various embodiments of the disclosure, in connection with the accompanying drawings, in which:

FIG. 1A is a perspective view depicting a buffer tube assembly and bolt carrier assembly of the prior art.

FIG. 1B is a cross-sectional view depicting a lower receiver and buffer tube assembly of the prior art.

FIG. 2A is a perspective view depicting a firearm buffer tube assembly, in accordance with a first embodiment of the disclosure.

FIG. 2B is a cross-sectional view of the firearm buffer tube assembly of FIG. 2A.

FIG. 3A is a perspective view depicting a firearm buffer tube assembly, in accordance with a second embodiment of the disclosure.

FIG. 3B is a cross-sectional view of the firearm buffer tube assembly of FIG. 3A.

FIG. 4A is a perspective view depicting a firearm buffer tube assembly, in accordance with a third embodiment of the disclosure.

FIG. 4B is a cross-sectional view of the firearm buffer tube assembly of FIG. 4A.

FIG. 5A is a perspective view depicting a firearm buffer tube assembly, in accordance with a fourth embodiment of the disclosure.

FIG. 5B is a cross-sectional view of the firearm buffer tube assembly of FIG. 5A.

While embodiments of the disclosure are amenable to various modifications and alternative forms, specifics thereof shown by way of example in the drawings will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims.

DETAILED DESCRIPTION

Referring to FIGS. 2A-2B, a first embodiment of a buffer tube 200 is depicted in accordance with the disclosure. The buffer tube 200 can generally be cylindrical in shape, having a distal end 202, a proximal end 204, and a tubular wall 206 extending therebetween. In production, the buffer tube 200 can be extruded, so as to include a raised rail portion 208 extending along an axial length of the cylindrical buffer tube 200. Undesirable portions of the raised rail portion 208, for example portion 208B, can be removed or otherwise machined away during further refinement. For example, in some versions, the remaining portion of the raised rail portion 208 can extend from the proximal end 204 forward, such that the raised rail portion 208 spans approximately two-thirds of the axial length of the buffer tube 200. A channel 210 and one or more blind bore apertures 212 can further be defined in the raised rail portion 208.

The tubular wall 206 can define tubular throughbore 214 traversing axially through the buffer tube 200. In some versions, the tubular wall 206 can have a substantially uniform thickness. In other embodiments, portions of the tubular wall 206 can be removed or otherwise machined away. For example, in one embodiment, a portion 216 of the tubular wall 206 in proximity to the distal end 202 can be machined away, for example, in a taper or a series of steps, such that the portion 216 of the tubular wall 206 in proximity to the distal end 202 has a smaller outer diameter than the buffer tube 200 in proximity to the proximal end 204. The portion 216 can further be machined to define external threads for selective coupling to the lower receiver (as depicted in FIG. 1B) and the castle nut (as depicted in FIG. 1A).

The proximal end 204 of the tubular throughbore 214 can be plugged via an endcap 218. As depicted in FIG. 2A-2B, the endcap 218 can be welded in place, thereby permanently and fixedly coupling the endcap 218 to the tubular wall 206. The endcap 204 can generally be cylindrical in shape, and can define at least one throughbore aperture 220, thereby enabling a venting of gas in the tubular throughbore 214 during reciprocation of the bolt carrier assembly and buffer (as depicted in FIG. 1A).

In one embodiment, the buffer tube 200, including the tubular wall 206 and the endcap 218, can be constructed of a high-strength, lightweight metal alloy, such as magnesium; although other alloys, such as aluminum, titanium can also be used. For example, in one embodiment, portions of the buffer tube 200 can be constructed of ZK60A magnesium; although other magnesium alloys are also contemplated.

The buffer tube 200 can further include an anodized surface coating to impart improved physical attributes to the surface of the buffer tube 200 including, for example improved abrasion resistance and increased surface lubricity. In one embodiment, micro-sized industrial diamond particles, nano-sized industrial garnet particles, silicon carbide, aluminum oxide, micro-sized Teflon™ spheres and/or a solid lubricant, such as molybdenum disulfide can be integrated into the anodized layer, for example via the methods and processes disclosed in U.S. Patent App. Ser. No. 62/827,502 (filed on Apr. 1, 2019), the disclosure of which is hereby incorporated herein by reference in its entirety.

Referring to FIGS. 3A-3B, a second embodiment of a buffer tube 300 is depicted in accordance with the disclosure. In some respects, the buffer tube 300 can share similarities with the first embodiment of the buffer tube 200. For example, the buffer tube 300 can generally be cylindrical in shape, having a distal end 302, a proximal end 304, and a tubular wall 306 defining a tubular throughbore 308 traversing axially through the buffer tube 300. The proximal end 304 of the tubular throughbore 308 can be plugged via an endcap 310.

As depicted in FIGS. 3A-3B, the endcap 310 can be threadedly coupled to the tubular wall 306. For example, interior threads 312 can be machined or otherwise manufactured into an interior diameter of the tubular wall 306. The endcap 310, which can be generally cylindrical in shape, can define a corresponding threaded portion 314, such that the endcap 310 can be threadedly coupled to the tubular wall 306, and selectively un-coupled from the tubular wall 306, if so desired for cleaning, maintenance and other purposes. The endcap 310 can further define a throughbore aperture 314, thereby enabling venting of gas in the tubular throughbore 308 during reciprocation of the bolt carrier assembly. In some embodiments, the throughbore aperture 314 can generally be in the shape of a hexagon thereby enabling threaded coupling and decoupling of the endcap 310 via an allen wrench or other similar tool; although other shapes are also contemplated. In another version of the second embodiment, the endcap 310 can be press fit into the tubular throughbore 308, so as to have an interference fit with the tubular wall 306.

Referring to FIGS. 4A-4B, a third embodiment of a buffer tube 400 is depicted in accordance with the disclosure. In some respects, the buffer tube 400 can share similarities with the first and second buffer tube embodiments 200, 300. For example, the buffer tube 400 can generally be cylindrical in shape, having a distal end 402, a proximal end 404, and a tubular wall 406 defining a tubular throughbore 408 traversing axially through the buffer tube 400. The proximal end 404 of the tubular throughbore 408 can be plugged via an endcap 410.

As depicted in FIGS. 4A-4B, the endcap 410 can be injection molded into the tubular throughbore 408 of the buffer tube 400, thereby blocking the proximal end 404 of the tubular throughbore 408. For example, in one embodiment, material can be injected through one or more inlets 412 defined in the tubular wall of the buffer tube 400. A distal flow gate 414A and a proximal flow gate 414B can be positioned on the respective distal and proximal ends of the intended endcap 410 prior to injection molding, such that upon the injection of material through the one or more inlets 412, the material can fill the space defined by the distal flow gate 414A, the proximal flow gate 414B and the inner diameter of the tubular wall 406. In some cases, the material can additionally fill a portion of the one or more inlet 412, and optional gas vents, which can be positioned opposite to the one or more inlet 412, thereby inhibiting the endcap 410 from shifting axially within the tubular throughbore 408. The endcap 410 can further define a throughbore aperture 416, thereby enabling venting of gas in the tubular throughbore 408 during reciprocation of the bolt carrier assembly. In some embodiments, either of the distal flow gate 414A and/or proximal flow gate 414B can include a protuberance 418 configured to form the throughbore aperture 416 during the injection molding process.

In other versions of the buffer tube 400, the endcap 410 can be selectively coupled to the tubular wall 406 via one or more fasteners, which can traverse through the tubular wall 406 and into the endcap 410. Removal of the one or more fasteners can enable selective uncoupling of the endcap 410 from the tubular wall 406, for cleaning, maintenance and other purposes.

Referring to FIGS. 5A-5B, a fourth embodiment of a buffer tube 500 is depicted in accordance with the disclosure. In some respects, the buffer tube 500 can share similarities with the first, second and third buffer tube embodiments 200, 300, 400. For example, the buffer tube 500 can be generally cylindrical in shape, having a distal end 502, a proximal end 504, and a tubular wall 506 defining a tubular throughbore 508 traversing axially through the buffer tube 500.

As depicted in FIGS. 5A-5B, the proximal end 504 can be bent, folded, or otherwise rolled over to effectively create an endcap 510, against which the buffer spring can exert reciprocal forces during operation of the firearm. In some embodiments, the proximal end 504 of the tubular wall 506 can be bent to approximate a 90° angle with respect to an axial length of the buffer tube 500, thereby effectively forming a continuous ring, wherein the center of the ring can enable the venting of gas in the tubular throughbore 508 during reciprocation of the bolt carrier assembly. In other versions, portions of the tubular wall 506 in proximity to the proximal end 504 can be removed to leave a plurality of tabs which can be bent to approximate a 90° angle with respect to an axial length of the buffer tube 500, thereby effectively forming a discontinuous ring. Angular configurations besides 90° are also contemplated.

Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions.

Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted.

Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended.

Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein.

For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. § 112(f) are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim. 

What is claimed is:
 1. A firearm buffer tube assembly, comprising: a magnesium alloy buffer tube having a distal end, a proximal end and a tubular wall defining a tubular throughbore traversing axially through the buffer tube between the distal end and the proximal end; and an endcap positioned at a proximal end of the buffer tube, thereby providing a buffer spring operating surface sufficient to resist reciprocation forces during operation.
 2. The firearm buffer tube assembly of claim 1, wherein the endcap is constructed of a magnesium alloy.
 3. The firearm buffer tube assembly of claim 1, wherein the endcap is welded to the buffer tube.
 4. The firearm buffer tube assembly of claim 1, wherein the endcap is press fit into the tubular throughbore, so as to have an interference fit with the tubular wall.
 5. The firearm buffer tube assembly of claim 1, wherein the endcap is threadably coupled to the buffer tube.
 6. The firearm buffer tube assembly of claim 1, wherein the endcap is injection molded into the buffer tube, such that a portion of the endcap extends through an aperture defined in the tubular wall, thereby inhibiting axial movement of the endcap.
 7. The firearm buffer tube assembly of claim 1, wherein the endcap is formed by bending a proximal portion of the tubular wall at an angle with respect to a longitudinal axis of the buffer tube to provide the buffer spring operating surface.
 8. The firearm buffer tube assembly of claim 1, wherein the endcap defines a throughbore aperture configured to enable venting of gas in the tubular throughbore during operation.
 9. The firearm buffer tube assembly of claim 1, wherein at least portions of the firearm buffer tube assembly include an anodized surface coating configured to impart improved abrasion resistance and increased surface lubricity.
 10. The firearm buffer tube assembly of claim 8, wherein at least one of micro-sized industrial diamond particles, nano-sized industrial garnet particles, silicon carbide, aluminum oxide, microsized Teflon™ spheres and/or molybdenum disulfide are integrated into the anodized surface coating.
 11. A method of constructing a firearm buffer tube assembly, comprising: extruding a magnesium alloy buffer tube having a distal end, a proximal end and a tubular wall defining a raised rail portion extending along an a longitudinal axis of the buffer tube, and a tubular throughbore traversing axially through the buffer tube between the distal end and the proximal end; removing a portion of the raised rail portion in proximity to the distal end of the buffer tube; defining external threads in proximity to the distal portion of the buffer tube; blocking a portion of the tubular throughbore in proximity to the proximal end of the buffer tube via an endcap, thereby providing a buffer spring operating surface sufficient to resist reciprocation forces during operation.
 12. The method of claim 11, wherein the endcap is constructed of a magnesium alloy.
 13. The method of claim 11, further comprising welding the endcap to the buffer tube.
 14. The method of claim 11, further comprising press fitting the endcap into the tubular throughbore, so as to create an interference fit with the tubular wall.
 15. The method of claim 11, further comprising threadably coupling the endcap to the buffer tube.
 16. The method of claim 11, further comprising injection molding the endcap into the buffer tube, such that a portion of the endcap extends through an aperture defined in the tubular wall, thereby inhibiting axial movement of the endcap.
 17. The method of claim 11, further comprising forming the endcap by bending a proximal portion of the tubular wall at an angle with respect to a longitudinal axis of the buffer tube to provide the buffer spring operating surface.
 18. The method of claim 11, further comprising defining a throughbore aperture in the endcap configured to enable venting of gas in the tubular throughbore during operation.
 19. The method of claim 11, further comprising providing an anodized surface coating over at least a portion of the firearm buffer tube assembly configured to impart improved abrasion resistance and increased surface lubricity.
 20. The method of claim 19, wherein at least one of micro-sized industrial diamond particles, nano-sized industrial garnet particles, silicon carbide, aluminum oxide, microsized Teflon™ spheres and/or molybdenum disulfide are integrated into the anodized surface coating. 